recovery of used lubricant oils through adsorption of residues on solid surfaces word

8/11/2019 Recovery of Used Lubricant Oils Through Adsorption of Residues on Solid Surfaces Word

1/12

BRAZILIANJOURNALOFPETROLEUM AND GAS |v.4n.3|p.091-102|2010|ISSN1982-0593

91

RECOVERY OF USED LUBRICANT OILS THROUGH ADSORPTION OF

RESIDUES ON SOLID SURFACES

ABSTRACTWaste lubricant oils are products that undergo degradation due to their use, yielding substances that are

potentially carcinogenic, such as PAHs (polycyclic aromatic hydrocarbons), which renders them improper.

In this work, a sequence of physical steps was investigated focusing on the adsorption on solids for PAHs

removal. Adsorption isotherms were constructed considering the PAHs concentration capacity presented

by different solids, with activated carbon as the most efficient adsorbent in the removal of PAHs. At the

end of the process it was possible to reestablish the main properties of the base oil, and to propose a

methodology for the recovery of the base oil, comprising solvent extraction, adsorption on solid surfacesand solvent distillation, making it adequate to be reintroduced into the production chain.

1To whom all correspondence should be addressed.

Address: Avenida dos Portugueses s/n - Campus Universitrio do Bacanga / CEP 65.040-080 / So Lus - Maranho - Brasil

Telephone: +55-98-3301-8266 / Fax: +55-98-3301-8245 | e-mail:[email protected]:10.5419/bjpg2010-0010

KEYWORDSlubricant oils; polycyclic aromatic hydrocarbons; adsorption; solvent extraction; recycling

aMoura, L. G. M.;

bAssuno Filho, J. L.;

aRamos, A. C. S.

1

aDepartamento deTecnologia Qumica,Centro deCincias Exatas eTecnologia,UniversidadeFederal do Maranho

bDepartamento dePs-Graduao emQumica,Centro deCincias Exatas eTecnologia,UniversidadeFederal do Maranho
mailto:[email protected]:[email protected]:[email protected]


2/12


92

1. INTRODUCTION

Lubricant base oils are mixtures that are

essentially formed by the fractions of petroleum

which are distilled between 300 C and 400 C

under atmospheric pressure, containing saturate

hydrocarbons and lower amounts of aromatic andnaphthenic compounds (Serrano et al., 2003;

Shishkin, 2006).

In order to obtain commercial lubricant oils,

base oils are mixed with additives which

particularize them or enhance some of their

characteristics. The role of these products is to

minimize wearing caused by physical friction, by

separating moving surfaces with the formation of a

thin resistant layer. This gives them a wide range of

applications on a variety of mechanical

equipments, namely industrial, automotive,

marine, railroads and hydraulic systems (Al-Ghouti

and Al-Atoum, 2007; Ramasamy and T-Raissi,

2007; Rauckyte and Hargreaves, 2006).

Lubricant oils are classified within the few

petroleum derivatives which are just partially

consumed during their use, with a limited usage

life term specified by the makers. After this period

of time, they become more prone to thermal

degradation and oxidation, thereby impairing their

use due to loss of lubricant ability, and requiringreplacement (Hamad et al., 2005; Raadnui and

Kleesuwan, 2005).

Used oils from mineral sources are not

biodegradable and contain materials produced in

the degradation of base oils, such as polycyclic

aromatic hydrocarbons (PAHs) with high viscosity;

oxygen compounds (organic acids, ketones); resins

and lacs; non-consumed additives; waste metals

from motors and lubricated machines, such as iron,

lead, chromium, barium and cadmium; and othercontaminants like water, non-burned fuel, dust and

various impurities which present risks to the

environment and to the public health (Rauckyte

and Hargreaves, 2006; Uar et al., 2005) . Oxidation

is the main degradation process, but due to the

natural complexity of these systems, the formation

of deposits and aromatic structures of high

molecular weight is still an elusive issue (Santos et

al., 2004).

Until now, it is well known that petroleum is a

limited non-renewable resource, hence processes

that allow for the prolongation of the oils usage life

term may be highly interesting for commercial and

environmental purposes.

In Brazil, the industrial operation which is used

to obtain base oils is called re-refining, aimed at

removing contaminants, degraded products and

additives from used oils in order to reestablish the

base lubricant oil characteristics, according to

specifications of the Brazilian Environmental

Council (Conselho Nacional do Meio Ambiente,

CONAMA). The Brazilian Agency of Petroleum,

Natural Gas and Biofuels (Agncia Nacional de

Petrleo, Gs Natural e Biocombustveis, ANP) is

the Brazilian institution in charge of the inspection,

collection and destination of the used lubricant

oils. According to the CONAMA resolution # 9, of

August 31, 1993, it constitutes crime to give a

different destiny to used oils such as discharge in

natural areas, commercialization, burning and

transportation other than the regulated re-refining

(CONAMA, 1993). Re-refined oils return to the

market, creating jobs, avoiding expenses and

minimizing environmental pollution.

Alternatives to industrial re-refining processes

are very valuable to obtain a product (base oil)

which, by proving to be more efficient and cheaper

than the conventional ones, could be reintroduced

in the production chain (Al-Ghouti and Al-Atoum,2007; Gmez-Rico et al., 2003; Sarrade et al.,

2001).

Some of the particulate materials found in the

waste oils can be removed by classical unit

operations, such as filtering and centrifugation;

however, some other undesirable substances

remain soluble and may occur in high

concentrations, thus decreasing the re-refining

efficiency. Recent studies have focused on particle

removal by solvent extraction as an essential step

in the global recovery process of used oils. It can be

noticed, however, that in this case it is still

necessary to conduct the re-refining in order to

obtain the base oil (Espada et al., 2008; Grieken et

al., 2008; Hamad et al., 2005).

Polycyclic aromatic hydrocarbons (PAHs) are

among the main soluble contaminants. Ramos et

al. (2001) evaluated the adsorption of petroleum

polyaromatic fractions, called asphaltenes and

resins, on the surface of different solids. Results

indicated that these fractions tend to concentrate

on the surface of different solids forming


3/12


93

multilayers. The interaction between the molecules

and the surface varies according to the adsorbent

chemical nature. Other studies (Mousavi-Dehghani

et al., 2004; Priyanto et al., 2001; Rincn et al.,

2007) also showed that these petroleum fractions

exhibit interfacial activity in aromatic solvents,

which may explain its tendency to adsorption.

Some oxide byproducts of used oils, such as the

PAHs, are chemically similar to the petroleum

heavy fractions, which makes the adsorption a

potential step to the removal of residues from used

lubricant oils (Arajo et al., 2008; Shaw, 1975).

In this work a sequence of physical steps was

designed to obtain base oils from used lubricant

oils, focusing on the removal of PAHs from used

oils through adsorption on solids of different

nature, such as activated carbon, rice husk, silica-

NH2, residues from acetylene synthesis, babau

epicarp and benzoin gum.

2. MATERIALS AND METHODS

2.1 Materials

The waste lubricant oil was collected in the city

of So Lus, in the State of Maranho (Brazil).

The solvents n-pentane (Carlo Erba, 99.5%), n-

hexane (Carlo Erba, 99.6%), n-heptane (Carlo Erba,

99.75%), toluene (Carlo Erba, 99.5%; F. Maia,

99.5%), ethanol (Merk, 99.8%; Isofar, 99.5%),

propan-2-ol (Reagen, 99.5%; Vetec, 99.5%), butan-

1-ol (Grupo Qumica, 99.5%; Reagen, 99.4%) and

terc-butanol (Vetec, 99.0%) were used to study the

solubility of the waste lubricant oils.

The adsorbents activated carbon, silica-gel, rice

husk, silica-NH2, residues from acetylene synthesis,

babau epicarp and benzoin gum were used in theadsorption tests. Activated carbon, silica gel and

alumina were also used in acidity determinations.

2.2 Preparation of a PAHs-concentrated

solid from the waste lubricant oil

Oil and butan-1-ol were mixed to a 1:2 ratio,

followed by 30 min stirring and 1 h centrifugation,

forming a biphasic system. The extract phase was

discharged and the remaining refined phase was

transferred to a Whatman # 42 filter paper, andthen to a soxhlet extractor in which the organic

material was extracted by continuous reflux with

toluene. Toluene was then distilled and evaporated

until a pastry material was obtained, which was

then transferred to a new filter paper and washed

in the soxhlet with pentane in order to extract the

residual oil. This practice was continued until the

refluxed solvent became clean. The pentane-

containing solution was replaced with pure toluene

in order to extract the remaining material from the

filter paper. The obtained solution was submitted

to distillation and evaporation so as to remove the

toluene, yielding a solid which was placed in a

dessicator for 24 h, before weighing.

2.3 Characterization of the PAHs-

concentrated solid (reference

material)

The solids obtained according to the procedure

described in section 2.2 were mixed with

spectroscopic potassium bromide (KBr) at a 1:10

ratio, followed by homogenization into a porcelain

melting pot and compression to 10 ton in order to

obtain a pastille, at 27 1 C. The pastille was then

placed in a Nicolet Nexus 470 FT-IR

spectrophotometer and the vibration spectra were

acquired.

2.4 Building of calibration curves for PAHs

quantification

Solutions of the solid (obtained as described in

section 2.3) were prepared in toluene at different

concentrations, attaining their respective scanning

spectrum in the UV-visible region. A Varian Cary50

Spectrophotometer with a 1 cm glass cell was used

to acquire absorbance curves as a function of the

concentration. A similar procedure was employed

to obtain the absorbance curves as a function of

the PAHs concentration in the systems with

mixtures of oil-alcohol (ethanol, propan-2-ol orbutan-1-ol).

2.5 Adsorption isotherms

Adsorption isotherms were constructed starting

with a fixed mass of adsorbent by varying the PAHs

concentrations in ethanol, propan-2-ol or butan-1-

ol. The solution/solid contact time was always

higher than the minimum time estimated in

adsorption kinetics studies carried out in this work.


4/12


94

2.6 Base oil recovery

Oil and alcohol (ethanol and propan-2-ol) were

mixed at a 1:2 ratio, stirred for 30 min and

centrifuged for 1 h, forming a biphasic system. The

supernatant was put in contact with the adsorbent

and, after equilibrium was reached, it was collected

and subjected to acidity tests (ASTM D3339-95) by

means of an A E536 Netron-Herisan Potentiograph

with a Netron 655 Dosimat automatic burette.

Lubricant oils were recovered from the

supernatant by means of fractionated distillation.

2.7 Determination of metals in the oil

samples

The amounts of Fe, Pb, Zn and Cu in the

recovered oil samples were determined by means

of atomic emission spectrometry according to the

procedure established by the ASTM D6595

method.

3. RESULTS AND DISCUSSION

3.1Preliminary remarks

Samples of the lubricant oils were employed as

received. Digital images of the novel and used oils,obtained through an Olympus BX 51/BX 52 Optical

Microscope, are shown in Figure 1. In Figure 1a it

can be observed that the sample is completely

clean, contrasting with Figure 1b, which depicts a

sample of used oil with much particulate material

formed by oil degradation and contamination. The

average size of the suspended particles of the

waste oil was determined as 1.0 0.1 m and no

evidence of emulsified water was identified.

Centrifugation of the waste oil samples (at a

maximum 4000 rpm in a Janetzki T32c centrifuge)

practically did not cause any reduction in the

amount of the suspended particulate material, as

observed with the optical microscope. Hence, two

strategies were adopted. Firstly, pentane and/or

heptane was added to the waste oil. These solvents

act as flocculants of heavy aromatic oil fractions.

The objective of this procedure was to increase

particles size, so that a positive response is

provoked in the natural sedimentation or in the

centrifugal field. In this study, a significant increase

in particle size was noticed, but it was not possible

to remove the particulate material from the waste

oil, even when centrifuged. The second strategy

was the addition of toluene, a renowned solvent

for crude oil and its derivatives, to reduce the

viscosity of the medium. The addition of toluene up

to 50 % in volume did not yield the desired

suspension separation. In particular, a large

amount of toluene would render any industrial

process economically unfeasible.

Facing the first negative test results, the next

step was to add substances that are partially

soluble in the waste oil, in order to generate a

biphasic system and estimate their efficiency in the

recovery of base oil from one of the phases. In the

estimated proportions, the systems with lubricant

oil added with alcohol (ethanol, propan-2-ol, terc-butanol and butan-1-ol) were soluble due to the

lack of emulsions when checked through the

optical microscope.

The formation of biphasic systems by adding

alcohol confirmed the possibility to develop a

procedure based on liquid-liquid extraction. Since

terc-butanol and butan-1-ol presented very close

results, butan-1-ol was chosen for the subsequent

(1a) (1b)

Figure 1. Digital images of the new (a) and waste (b) lubricant oils (400 times magnification).


5/12


95

experiments, particularly because it is less

expensive. In these systems, the suspended

particles in the waste oil were concentrated in the

lower phase (lees), whilst the bulk of the base

lubricant oil was concentrated in the upper,

supernatant phase. Supernatants of used oil mixed

with ethanol, propan-2-ol and butan-1-ol were

used to evaluate the adsorption of soluble

polyaromatic residues on different solids. In order

to quantify the transfer of the PAHs from the

supernatants to the solid surfaces, it was initially

necessary to establish a method that allowed the

monitoring of PAHs, and for that purpose the

technique used was molecular adsorption

spectrophotometry in the UV-visible region.

3.2PAHs characterization and

quantificationThe particulate material (phase containing lees)

was submitted to a treatment in order to obtain a

solid with high concentration of PAHs, as explained

in Section 2.2.

It is useful to note that, in the characterization

of the reference sample by the FT-IR technique, it

was not possible to get a fair homogenization of

the reference material with KBr to acquire the

vibration spectra. This probably caused the

transmittance interval to remain unfit within thedesired range of values (30 to 70 %) (Silvestein and

Webster, 1997). Nevertheless, this result did not

impair the PAHs qualitative analysis.

Analysis of Figure 2 allowed the identification of

some characteristic bands of systems containing

polyaromatic hydrocarbons, typically in three

spectral regions and in accordance with specific

references (Silvestein and Webster, 1997).

25

24

23

22

21

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Wave number (cm-1)

Figure 2. Infrared vibration spectrum (FT-IR) of the

reference sample after washing with n-pentane.

24.7

24.6

24.5

24.4

24.3

24.2

24.1

24.0

23.9

23.8

600 650 700 750 800 850 900 950

Wave number (cm-1

)


reference sample after washing with n-pentane.

However, it is noticeable that, when dealing with a

sample with high polidispersity, strong dependence

with the medium (surroundings) can occur, asshown by the shape and distribution of the bands.

The first band is attributed to aromatic C-H axial

deformation vibrations, which occur between 3000

and 3100 cm-1

; methyl axial deformation can be

detected at 2965, 2940, 2918 and 2875 cm-1

,

comprising the A region in Figure 2.

The second important band in the

characterization of PAHs is formed by a set of

peaks between 1500 and 1630 cm-1

related to the

C=C axial deformation of the aromatic ring (the B

region in Figure 2). There is also a region between

1000 and 1300 cm-1

(C) where a wide band can

be observed due to C-H angular deformation in the

plane. Finally, the D region, from 675 to 900cm-1

,

refers to the angular deformation of the C-H bound

planes of the aromatic ring. In order to allow for

better peak interpretation, this region can be seen

in a separate graph (Figure 3).

Taking into account that the reference solid is

formed by a polydisperse sample, it was also

decided to investigate the FT-IR spectrum afterwashing with hexane. This was also justified by the

fact that hexane is a substance typically used in the

extraction of oils, especially those of vegetable

origin. The FT-IR spectrum of the reference sample

after washing with hexane is shown in Figure 4. The

experiment was conducted in similar conditions to

those of the reference sample after washing with

pentane.

In Figure 4, a similarity can be verified between

the FT-IR spectra of both reference samples by theoccurrence of the same bands that characterize

D

BA

C

2940

10651618

1466and1498

2365

741

Transmitance(%)

Transmitance(%)


6/12


96

D

AB

C

aromatic and polyaromatic compounds, although

this is more prominent in Figure 4. Since the

purpose of this work is to use the samples as

parameters to evaluate the PAHs transfer in the

process of adsorption on solid surfaces, these

results were considered reasonably qualitative.

Scanning spectra of the PAHs-rich solid

solubilized in toluene (concentrations of 0.03; 0.10;

0.25; e 0.50 g.L-1

) were obtained in the UV-visible

region at room temperature (27 1 C). In order to

better view the region of interest, the spectra

depicted in Figure 5 shows only the bands between

320 and 720 nm. Lack of adsorption peaks was

observed on the curves, a typical behavior of

polydisperse systems.

96

94

92

90

88

86

84

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Wave number (cm-1)


reference sample after washing with n-hexane.

The 350 and 400 nm wavelengths were selected

to study the PAHs in the supernatant, mainly based

upon similar studies using asphaltene and resin

solutions (crude oil polyaromatic fractions) in

aromatic solvents (Chang and Fogler 1993; Ramos

et al., 2001).

Two calibration curves were built, at 350 and

400 nm, proceeding with concentrations at which

the maximum signal of 2 adsorption units was

obtained, so as to minimize deviation from ideality,

according to information available in the literature

(Chang and Fogler 1993; Ramos et al., 2001) . Both

curves exhibited similar behavior, revealing good

linearity between adsorption and PAHs

concentration. Improved linearity was obtained at

350 nm; therefore, this wavelength was selected in

this work to determine the amount of PAHs in

toluene, since it produced a correlation coefficient

value that was closest to unity. However, if the

accuracy in the concentration measurement is

considered in both cases, the coefficients are

equally close to 1.0.

The curve of absorbance (A) as a function of

concentration (C), given by the equation A =

3.42742 C 0.00568, was used to determine the

amount of PAHs in the supernatant phases of other

systems. To estimate the correlation between the

PAHs concentrations in toluene and the

concentrations in the other systems, PAHs

calibration curves in alcohols were built using the

respective supernatants.

It was proved that the scanning spectra of the

PAHs in alcohols did not present defined peaks in

the visible region, with behavior similar to the one

observed in the toluene curves. The readings were

recorded considering adsorption levels lower than2, in good agreement with the Lambert-Beer law.

In Table 1 the equations originated from the

calibrations curves of the PAHs in the evaluated

alcohols are presented.

From Table 1, it was possible to extract the

values of the molar absortivity: 0.46463 for

ethanol, 0.859460 for propan-2-ol and 1.08387 for

butan-1-ol. These values differ from one another

and also from the one found for toluene (3.42742),

indicating the effects of the medium on the PAHssolubility. Therefore, it is not possible to establish a

Table 1. Equations from the calibration curves of PAHs in alcohols (ethanol, propan-2-ol and butan-1-ol) at

27 1 C.

Solvent Equation Correlation Coefficient (R2)

Ethanol A = 0.46463 C + 0.0241 0.99911

Propan-2-ol A = 0.85946 C + 0.1565 0.99997

Butan-1-ol A = 1.08387 C + 0.0184 0.99980

Transmitance(%)


7/12


97

precise correlation for the determination of the

PAHs concentration; however a relationship

between the absorbance and concentration can be

applied to quantify the variation in the PAHs mass

for all systems.

3.3Adsorption isotherms

After defining the methodology for monitoring

the PAHs concentration in the supernatants, the

next step was to estimate the different solids

adsorption capacity (activated carbon, rice husk,

silica-NH2, residues from acetylene synthesis,

babau epicarp and benzoin gum) with respect to

PAHs. To do so, first a study was performed on the

adsorption kinetics in each system aiming at the

determination of the equilibrium time. The

experiments were conducted starting from three

initial concentrations. The most concentratedsystem was prepared at a 2:1 ratio of solvent and

waste oil, in that order, without dilution. The plots

in Figures 5 and 7 to 11 refer only to solutions with

higher concentration for each solvent, since the

remaining solutions with other concentrations

presented the same behavior.

Figure 5 shows the adsorption kinetics for the

supernatants of the oil-alcohol systems on

activated carbon. The initial concentration

decreases slowly until reaching equilibrium inabout 72 h. This result, in principle, is irrespective

of the nature of the solvent. This balancing time

was also found in the studies by Assuno Filho

(2004) for equivalent systems, which reinforces the

validity of the results obtained here.

The fact that the initial PAHs concentration is

different for each system proves that the base oil

solubility depends on the nature of the alcohol.

Taking into account that the volume of the phases

differed according to the sequence butan-1-ol >

propan-2-ol > ethanol, it was possible to conclude

that, in this case, the best solvent to extract base

oil starting from used oil is butan-1-ol, followed by

propan-2-ol and ethanol. The period of 72 h

suggests slow transference kinetics for the PAHs

adsorption process over activated carbon, and the

same period of time was measured for other solids.

Figure 6 presents the adsorption isotherms for

the activated carbon system in different solvents.

An increase in the surface concentration occurs

with increasing equilibrium concentration. The

isotherms behavior suggests enhanced adsorption

in the systems with ethanol, followed by propan-2-

ol and butan-1-ol. That result is in good agreement

with the higher PAHs solubility in the butan-1-ol

and with studies that indicate a more effective

adsorption of that sort of compounds, when using

rather polar solvents (Dubey and Waxman, 1991;

Jiao et al., 2007). Moreover, this points out at a

potential technological application of this solid to

remove part of the PAHs from used lubricant oils.

The isotherms reported by Assuno Filho (2004)

clearly suggest an L2-type physical adsorption

(Myers, 1999), corresponding to a multilayerformation process that is, in principle, slightly

different from the ones presented in this article,

which show a less evident tendency. In this study,

within the concentration range assessed, the

results indicate that there is still a large area

available for adsorption and, therefore, solids

saturation did not occur.

50

Activated carbon

45 Ethanol

Propan-2-ol40 Butan-1-ol

35

30

25

20

15

10

700

600

500

400

300

200

100

0

Activated carbon

Ethanol

Propan-2-ol

Butan-1-ol

-20 0 20 40 60 80 100 120 140 160 180

Time (h)

Figure 5. Supernatant concentrations of oil/ethanol,

oil/propan-2-ol and oil/butan-1-ol systems as afunction of adsorption time over activated carbon at

350 nm and 28 1 C.

0 5 10 15 20 25 30 35 40

Equilibrium concentration (gL-1)

Figure 6. Adsorption isotherms of PAHs over

activated carbon in oil/ethanol, oil/propan-2-ol andoil/butan-1-ol systems at 28 1 C.

Concentration

(gL-1)

AdsorbedPAH

(mgg

-1)


8/12


98

50

Rice husk

45 Ethanol

Propan-2-ol40 Butan-1-ol

35

30

25

20

15

10

-20 0 20 40 60 80 100 120 140 160 180

Figure 7 presents a study of PAHs adsorption

kinetics on rice husk, and the results found are, in

principle, similar to the ones presented by

activated carbon. Again the observed sequence of

enhanced base oil extraction was butan-1-ol >

propan-2-ol > ethanol. A tendency to reach the

equilibrium concentration around 48 h was

observed, however, from which point there is a

further increase in the PAHs concentration in the

supernatant. Since each experiment in this work

Time (h)


oil/propan-2-ol and oil/butan-1-ol systems as a

function of adsorption time over rice husk at 28 1C

The industrial application of this solvent can be

extended for the removal of polyaromatic

hydrocarbons in crude oil fluids, taking into

account that there have been similar results

reported on asphaltene adsorption in toluene over

activated carbon (Ramos et al., 2001). This solid is

obtained from organic materials (such as wood

powder, vegetal carbon, crude oil coke and

bitumen) and the activation is a physical

modification that augments its surface area by

removing natural hydrocarbons, which can confirm

the affinity derived from chemical similarity with

the adsorbates. Moreover, physical adsorption is

principally based upon van der Waals forces and

weak bonds emerged from the formation of a

dipole momentum in the particles due to electron

dislocations. The surface of activated carbon is

plenty of free charges, generated mainly during the

activation process, a feature that enhances the

adsorption effects with aromatic compounds,

which are scarcely polar but present resonance

that turns them more susceptible to formation of

dipole momentum. In view of this, the higher

efficacy of activated carbon in PAHs adsorption can

be justified mainly because of its nature (Ahmedna

et al., 2000; Lszl et al., 1997; Shreve and Brink

Jr., 1997).

Adsorption studies were carried out with other

solids, such as rice husk, which has some

characteristics that render it as potential PAHs

adsorbent, namely the occurrence of hydroxyl

functional groups on its surface (Ahmedna et al.,

2000; Lszl et al., 1997). This is also the case with

solid chitosan, which has been reported as a good

candidate to concentrate PAHs (Assuno Filho,2004).

was carried out at least three times, such behavior

is not a consequence of an analytical error, but is

probably due to PAHs desorption as a result of

modifications on the surface of rice husk by

reaction with solvent or changes in the medium

acidity, as confirmed by further tests. Ajmal et al.

(2003) used this solid for metal adsorption, and

described the use of acids in the desorption step,

which can be based not only in the solubilization of

those metals, but also in a solid surface change and

in the inhibition of active sites. This result

represents a negative aspect for the use of rice

husk as PAHs adsorbent and, in this work, such

aspect was considered to interrupt its

investigation.

Figures 8 through 11 present the results of

kinetics studies on PAHs adsorption over different

adsorbents, namely modified silica, the soot

formed during acetylene synthesis, babau epicarpand benzoin gum. All the experiments were done in

triplicate and the results were very similar. For this

reason, the graphs were constructed employing

the average value of each determination.

The tested silica was modified by doping with

nitrogen compounds (Farias and Airoldi, 2000a;

Farias and Airoldi, 2000b) and its selection was

due to the presence of amine (-NH2), which, like

the hydroxyl group, is possibly one of the active

sites present in chitosan, a solid which was quiteeffective in PAHs adsorption (Assuno Filho,

2004). The soot formed during acetylene synthesis

and the babau epicarp are abundant industrial by-

products and their utilization as adsorbents can

have reasonable economical viability. The benzoin

gum is a resin extracted from plants belonging to

the Styracaceae family, so far used as fixer in the

cosmetics industry and as precursor of other

products in the pharmaceutical industry.

Absorbance capacity and low price could represent

favorable parameters to determine the use ofthese solids as adsorbents.

Conc

entration(gL-1)


9/12


99

Silica modified

with NH2

Ethanol

Propan-2-ol

Butan-1-ol

45

40

35

30

25

20

15

10

Benzoin gum

Ethanol

Propan-2-ol

Butan-1-ol

Concentration(gL-1)

Nevertheless, the results found showed that a

slight variation occurred in the PAHs concentration

in the supernatant as a function of time, which

indicates that, in this case and under these

conditions, these solids seem to be less

50

-20 0 20 40 60 80 100 120 140 160 180

Time (h)

Figure 8. Supernatant concentrations of oil/ethanol,oil/propan-2-ol and oil/butan-1-ol systems as a

function of adsorption time over silica modified with

NH2, at 350 nm and 28 1 C.

50

Residues from45

Acetylene

synthesis40

Ethanol

35 Propan-2-olButan-1-ol

30

25

20

15

10

-20 0 20 40 60 80 100 120 140 160 180

Time (h)



function of adsorption time over residues from

acetylene synthesis, at 350 nm and 28 1 C.

appropriate than activated carbon to adsorption

operations.

Recovered oils were obtained by solvent

evaporation after the adsorption process on solids.

In his studies, however, Assuno Filho (2004)

obtained high acidity index values at the end of the

lubricant oils recovery process. In this article, in

order to determine the acidity, two systems,

namely the samples of oil/ethanol after adsorption

over activated carbon and oil/propan-2-ol after

adsorption over silica gel, were put in contact with

alumina, a solid with alkaline characteristics that

may act as neutralizing agent. The acidity indices of

these two systems were determined before and

after conducting this procedure (contact with

alumina), making possible the calculation of the

acidity variation.

These systems were selected because they

presented better adsorption results and the

neutralizing effects could be extended to other

systems. However, tests for the determination of

this index showed that the variation rate was only

0.5 % in the oil extracted by ethanol and treated

with activated carbon, and 6.7 % in the oil

extracted by propan-2-ol and treated with silica

gel. After solvent distillation, the recovered base

oils still presented rather high acidity indices,

compared to the levels established by theprocedure ASTM D974 and specified by ANP, as

shown in Table 2.

These results indicate that alumina is not

recommended for the neutralization step of the

global recovery process. A viable alternative for

acid number correction would be the process

50 30

Ba bau

45 epicarpEthanol

40Propan-2-olButan-1-ol

35

30

25 15

20

15 10

-20 0 20 40 60 80 100 120 140 160 180

Time (h)

Figure 10. Supernatant concentrations of

oil/ethanol, oil/propan-2-ol and oil/butan-1-ol

systems as a function of adsorption time over babau

epicarp, at 350 nm and 28 1 C.

-20 0 20 40 60 80 100 120 140 160 180

Time (h)



function of adsorption time over benzoin gum, at 350nm and 28 1 C.

-1

Con

centration

(gL

)

Concentration

(gL-

1)

Concentration(gL-1)

25


10/12


100

Table 2. ASTM and experimental acid numbers of recovered lubricant base oil samples.

Solvent used in base oil

extraction

Ethanol

Acid Number mg KOH/g)

ASTM D974)

0.05

Acid Number mg KOH/g)

Experimental

6.593

Propan-2-ol 2.994

currently employed in the industry, which uses

alkaline substances that are able to neutralize

undesirable acid compounds found in the oil.

However, in general, the process presented here

for the recovery of waste lubricant oils showed an

improvement on the quality of the final products

on various aspects, such as reduction on both

viscosity and PAHs content, indicating its potential

as an industrial process for the treatment of usedoils.

It must be observed, however, that some

aspects of the proposed global process of used

lubricant oil recovery were not evaluated in this

study. The recovery of the adsorbents by

desorption of the PAHs, for example, was not

investigated and should be considered in further

studies with more detail, since this is an important

aspect concerning environmental preservation.

4. CONCLUSIONS

In this article, a sequence of physical steps

(solvent extraction, adsorption on solid surfaces

and solvent distillation) was presented aiming to

reestablish the main properties of base oils, with a

focus on the stage of removal of PAHs by

adsorption on different solid surfaces that are

commonly used as adsorbents of PAHs, such as

activated carbon and silica (in this case, silicamodified with NH2), and other alternative solids,

such as rice husk, residues from acetylene

synthesis, babau epicarp and benzoin gum. These

alternative solids, however, did not provide a high

capacity to concentrate PAHs on their surface

when compared with the classical adsorbents

investigated.

Butan-1-ol presented better efficacy as

extraction agent of base lubricant oils, followed by

propan-2-ol and ethanol. The methodology for

quantifying the PAHs yielded good results, allowing

the determination of the PAHs mass variation in

the solutions with various solvents by means of

calibration curves obtained with toluene.

The adsorption isotherms indicated that

activated carbon has a great potential for

concentrating PAHs molecules on its surface and,

hence, can be used in industrial applications with

that purpose. The best system for PAHs

concentration comprised activated carbon and

ethanol. The recovered oils presented high acid

number and solid alumina was not efficient in the

correction of this index.

Based upon these results, three main different

steps can be viewed as possibly feasible for the

recovery process of used lubricant oils: (a)

extraction with solvent, (b) adsorption over solids

and (c) solvent distillation. Nonetheless, further

studies are still required for the improvement of

the global process.

5. REFERENCESAhmedna, M.; Marshall, W. E.; Rao, R. M.

Production of granular activated carbons from

select agricultural by-products and evaluation of

their physical, chemical and adsorption

properties. Bioresource Technology, v. 71, p. 113-

123, 2000.doi:10.1016/S0960-8524(99)00070-X

Ajmal, M.; Rao, R.A.K.; Anwar, S.; Ahmad, J.;

Ahmad, R. Adsorption studies on rice husk:removal and recovery of Cd(II) from

wastewater. Bioresource Technology, v. 86, p. 147-

149, 2003.doi:10.1016/S0960-8524(02)00159-1

Al-Ghouti, M.A.; Al-Atoum, L. Virgin and recycled

engine oil differentiation: A spectroscopic study.

Journal of Environmental Management, v. 90, p.

187-195, 2007. doi:10.1016/j.jenvman.2007.08.018

Arajo, R. S.; Azevedo, D. C. S.; Cavalcante Jr., C. L.;

Jimnez-Lpez, A.; Rodrguez-Castelln, E.

Adsorption of polycyclic aromatic hydrocarbons

(PAHs) from isooctane solutions by mesoporous
http://dx.doi.org/10.1016/S0960-8524(99)00070-Xhttp://dx.doi.org/10.1016/S0960-8524(99)00070-Xhttp://dx.doi.org/10.1016/S0960-8524(99)00070-Xhttp://dx.doi.org/10.1016/S0960-8524(02)00159-1http://dx.doi.org/10.1016/S0960-8524(02)00159-1http://dx.doi.org/10.1016/S0960-8524(02)00159-1http://dx.doi.org/10.1016/j.jenvman.2007.08.018http://dx.doi.org/10.1016/j.jenvman.2007.08.018http://dx.doi.org/10.1016/j.jenvman.2007.08.018http://dx.doi.org/10.1016/j.jenvman.2007.08.018http://dx.doi.org/10.1016/S0960-8524(02)00159-1http://dx.doi.org/10.1016/S0960-8524(99)00070-X


11/12


101

molecular sieves: Influence of the surface

acidity. Microporous and Mesoporous

Materials, v. 108, p. 213-222, 2008.

doi:10.1016/j.micromeso.2007.04.005

forms synthesized from neutral amine route.

Colloids and Surfaces A: Physicochemical and

Engineering Aspects, v. 172, p. 145-152, 2000b.

doi:10.1016/S0927-7757(00)00577-X

Assuno Filho, J. L. Processo de recuperao de

leos lubrificantes bsicos, atravs da adsoro

de HPAs sobre slidos de diferentes naturezas.

Dissertao de Mestrado. Programa de Ps-

Graduao em Qumica, Universidade Federal

do Maranho, 2004. (in Portuguese).

Brggemann, O.; Freitag, R. Determination of

polycyclic aromatic hydrocarbons in soil

samples by micellar electrokinetic capillary

chromatography with photodiode-array

detection. Journal of chromatography A, v. 717,

p. 309-324, 1995. doi:10.1016/0021-

9673(95)00536-X

Gmez-Rico, M.F.; Martn-Gulln, I.; Fullana, A.;

Conesa, J.A.; Font, R. Pyrolysis and combustion

kinetics and emissions of waste lube oils.

Journal of Analytical and Applied Pyrolysis, v.

68-69, p. 527-546, 2003. doi:10.1016/S0165-

2370(03)00030-5

Grieken, R.; Coto, B.; Pea, J.L.; Espada, J.J.

Application of a generalized model to the

estimation of physical properties and

description of the aromatic extraction from a

highly paraffinic lubricating oil. Chemical

Engineering Science, v. 63, p. 711-720, 2008.

doi:10.1016/j.ces.2007.10.013

Chang, C.-L.; Fogler, H. S. Asphaltene stabilization

in alkyl solvents using oil-soluble amphiphiles,

In: SPE International Symposium on Oilfield

Chemistry, Society of Petroleum Engineers,

1993, p. 339-345.doi:10.2118/25185-MS

CONAMA. Resoluo No

9, 31 de agosto de 1993.

Dispe sobre leos lubrificantes e atividades de

gerenciamento correspondentes. Conselho

Nacional do Meio Ambiente, 1993. Available at:http://www.mma.gov.br/port/conama/res/res9

3/res0993.html. Accessed on: 10/08/2010. (in

Portuguese).

Dubey, S. T., Waxman, M. H. Asphaltene adsorption

and desorption from mineral surfaces. SPE

Reservoir Engineering, v. 6, p.389-395, 1991.

doi:10.2118/18462-PA

Espada, J. J.; Coto, B.; van Grieken, R.; Moreno, J.

M. Simulation of pilot-plant extraction

experiments to reduce the aromatic content

from lubricating oils. Chemical Engineering and

Processing, v. 47, p. 1398-1403, 2008.

doi:10.1016/j.cep.2007.06.012

Farias, R. F.; Airoldi, C. Mechanically induced

structural modifications in metal-doped lamellar

silica. Journal of Non-Crystalline Solids, v. 261,

p. 181-185, 2000a. doi:10.1016/S0022-

3093(99)00595-5

Farias, R. F.; Airoldi, C. Thermochemical features oflamellar silica, copper, nickel and cobalt-doped

Hamad, A.; Al-Zubaidy, E.; Fayed, M. E. Used

lubricating oil recycling using hydrocarbon

solvents. Journal of Environmental

Management, v. 74, p. 153-159, 2005.

doi:10.1016/j.jenvman.2004.09.002

Jiao, X. C.; Xu, F.L.; Dawson, R.; Chen, S. H.; Tao, S.

Adsorption and absorption of polycyclic

aromatic hydrocarbons to rice roots.

Environmental Pollution, p. 148, v. 230-235,2007.

Lszl, K.; Bta, A.; Nagy, L. G. Characterization of

activated carbons from waste materials by

adsorption from aqueous solutions. Carbon, v.

35, p. 593-598, 1997. doi:10.1016/S0008-

6223(97)00005-5

Mousavi-Dehghani, S. A.; Riazi, M. R.; Vafaie-Sefti,

M.; Mansoori, G. A. An analysis of methods for

determination of onsets of asphaltene phase

separations. Journal of Petroleum Science and

Engineering, v. 42, p. 145-156, 2004.

doi:10.1016/j.petrol.2003.12.007

Myers, D. Surfaces, interfaces, and colloids

principles and applications, New York: Wiley-

VCH, 1999. doi:10.1002/0471234990

Priyanto, S.; Mansoori, G. A.; Suwono, A.

Measurement of property relationships of nano-

structure micelles and coacervates of

asphaltene in a pure solvent. Chemical
http://dx.doi.org/10.1016/j.micromeso.2007.04.005http://dx.doi.org/10.1016/j.micromeso.2007.04.005http://dx.doi.org/10.1016/S0927-7757(00)00577-Xhttp://dx.doi.org/10.1016/S0927-7757(00)00577-Xhttp://dx.doi.org/10.1016/0021-9673(95)00536-Xhttp://dx.doi.org/10.1016/0021-9673(95)00536-Xhttp://dx.doi.org/10.1016/0021-9673(95)00536-Xhttp://dx.doi.org/10.1016/0021-9673(95)00536-Xhttp://dx.doi.org/10.1016/S0165-2370(03)00030-5http://dx.doi.org/10.1016/S0165-2370(03)00030-5http://dx.doi.org/10.1016/S0165-2370(03)00030-5http://dx.doi.org/10.1016/S0165-2370(03)00030-5http://dx.doi.org/10.1016/j.ces.2007.10.013http://dx.doi.org/10.1016/j.ces.2007.10.013http://dx.doi.org/10.2118/25185-MShttp://dx.doi.org/10.2118/25185-MShttp://dx.doi.org/10.2118/25185-MShttp://www.mma.gov.br/port/conama/res/res93/res0993.htmlhttp://www.mma.gov.br/port/conama/res/res93/res0993.htmlhttp://www.mma.gov.br/port/conama/res/res93/res0993.htmlhttp://dx.doi.org/10.2118/18462-PAhttp://dx.doi.org/10.2118/18462-PAhttp://dx.doi.org/10.1016/j.cep.2007.06.012http://dx.doi.org/10.1016/j.cep.2007.06.012http://dx.doi.org/10.1016/S0022-3093(99)00595-5http://dx.doi.org/10.1016/S0022-3093(99)00595-5http://dx.doi.org/10.1016/S0022-3093(99)00595-5http://dx.doi.org/10.1016/S0022-3093(99)00595-5http://dx.doi.org/10.1016/j.jenvman.2004.09.002http://dx.doi.org/10.1016/j.jenvman.2004.09.002http://dx.doi.org/10.1016/S0008-6223(97)00005-5http://dx.doi.org/10.1016/S0008-6223(97)00005-5http://dx.doi.org/10.1016/S0008-6223(97)00005-5http://dx.doi.org/10.1016/S0008-6223(97)00005-5http://dx.doi.org/10.1016/j.petrol.2003.12.007http://dx.doi.org/10.1016/j.petrol.2003.12.007http://dx.doi.org/10.1002/0471234990http://dx.doi.org/10.1002/0471234990http://dx.doi.org/10.1002/0471234990http://dx.doi.org/10.1002/0471234990http://dx.doi.org/10.1016/j.petrol.2003.12.007http://dx.doi.org/10.1016/S0008-6223(97)00005-5http://dx.doi.org/10.1016/S0008-6223(97)00005-5http://dx.doi.org/10.1016/j.jenvman.2004.09.002http://dx.doi.org/10.1016/S0022-3093(99)00595-5http://dx.doi.org/10.1016/S0022-3093(99)00595-5http://dx.doi.org/10.1016/j.cep.2007.06.012http://dx.doi.org/10.2118/18462-PAhttp://www.mma.gov.br/port/conama/res/res93/res0993.htmlhttp://www.mma.gov.br/port/conama/res/res93/res0993.htmlhttp://dx.doi.org/10.2118/25185-MShttp://dx.doi.org/10.1016/j.ces.2007.10.013http://dx.doi.org/10.1016/S0165-2370(03)00030-5http://dx.doi.org/10.1016/S0165-2370(03)00030-5http://dx.doi.org/10.1016/0021-9673(95)00536-Xhttp://dx.doi.org/10.1016/0021-9673(95)00536-Xhttp://dx.doi.org/10.1016/S0927-7757(00)00577-Xhttp://dx.doi.org/10.1016/j.micromeso.2007.04.005


12/12


102

Engineering Science, v. 56, p. 6933-6939, 2001.

doi:10.1016/S0009-2509(01)00337-2

Raadnui, S.; Kleesuwan, S. Low-cost condition

monitoring sensor for used oil analysis. Wear, v.

259, p. 1502-1506, 2005.

doi:10.1016/j.wear.2004.11.009

Ramasamy, K. K.; T-Raissi, A. Hydrogen production

from used lubricating oils. Catalysis Today, v. 129,

p. 365-371, 2007. doi:10.1016/j.cattod.2006.09.037

Ramos, A. C. S.; Haraguchi, L.; Notrispe, F. R.; Loh,

W.; Mohamed, R. S. Interfacial and colloidal

behavior of asphaltenes obtained from Brazilian

crude oils. Journal of Petroleum Science and

Engineering, v. 32, p. 201-216, 2001.

doi:10.1016/S0920-4105(01)00162-0

Rauckyte, T.; Hargreaves, D. J.; Pawlak, Z.

Determination of heavy metals and volatile

aromatic compounds in used engine oils and

sludges. Fuel, v. 85, p. 481-485, 2006.

doi:10.1016/j.fuel.2005.08.004

Rincn, J.; Caizares, P.; Garca, M. T. Regeneration

of used lubricant oil by ethane extraction. The

Journal of Supercritical Fluids, v. 39, p. 315-322,

2007. doi:10.1016/j.supflu.2006.03.007

Santos, J. C. O.; dos Santos, I. M. G.; Souza, A. G.;

Sobrinho, E. V.; Fernandes Jr., V. J.; Silva, A. J. N.

Thermoanalytical and rheological

characterization of automotive mineral

lubricants after thermal degradation. Fuel, v. 83,

p. 2393-2399, 2004. doi:10.1016/j.fuel.2004.06.016

Sarrade, S.; Schrive, L.; Gourgouillon, D.; Rios, G. M.

Enhanced filtration of organic viscous liquids by

supercritical CO2 addition and fluidification.

Application to used oil regeneration. Separation

and Purification Technology, v. 25, p. 315-321,

2001. doi:10.1016/S1383-5866(01)00058-2

Serrano, D. P.; Aguado, J.; Escola, J. M.; Garagorri,

E. Performance of a continuous screw kiln

reactor for the thermal and catalytic conversion

of polyethylene-lubricating oil base mixtures.

Applied Catalysis B: Environmental, v. 44, p. 95-

105, 2003. doi:10.1016/S0926-3373(03)00024-9

Shaw, D. J. Introduo qumica dos colides e de

superfcies. So Paulo: Edgard Blcher, 1975. (in

Portuguese).

Shishkin, Y.L. A new quick method of determining

the group hydrocarbon composition of crude

oils and oil heavy residues based on theiroxidative distillation (cracking) as monitored by

differential scanning calorimetry and

thermogravimetry. Thermochimica Acta, v. 440,

p. 156-165, 2006.doi:10.1016/j.tca.2005.11.008

Shreve, R. N.; Brink Jr., J. A. Indstrias de processos

qumicos. Rio de Janeiro: Guanabara Koogan

S.A., 1997. (in Portuguese).

Silvestein, R. M.; Webster, F. X. Spectrometric

identification of organic compounds. New York:John Wiley and Sons, 1997.

Uar, S.; Karagz, S.; Yanik, J.; Saglam, M.; Yuksel,

M. Copyrolysis of scrap tires with waste

lubricant oil. Fuel Processing Technology, v. 87,

p. 53-58, 2005.doi:10.1016/j.fuproc.2005.06.001
http://dx.doi.org/10.1016/S0009-2509(01)00337-2http://dx.doi.org/10.1016/S0009-2509(01)00337-2http://dx.doi.org/10.1016/j.wear.2004.11.009http://dx.doi.org/10.1016/j.wear.2004.11.009http://dx.doi.org/10.1016/j.cattod.2006.09.037http://dx.doi.org/10.1016/j.cattod.2006.09.037http://dx.doi.org/10.1016/S0920-4105(01)00162-0http://dx.doi.org/10.1016/S0920-4105(01)00162-0http://dx.doi.org/10.1016/j.fuel.2005.08.004http://dx.doi.org/10.1016/j.fuel.2005.08.004http://dx.doi.org/10.1016/j.supflu.2006.03.007http://dx.doi.org/10.1016/j.supflu.2006.03.007http://dx.doi.org/10.1016/j.supflu.2006.03.007http://dx.doi.org/10.1016/j.fuel.2004.06.016http://dx.doi.org/10.1016/j.fuel.2004.06.016http://dx.doi.org/10.1016/j.fuel.2004.06.016http://dx.doi.org/10.1016/S1383-5866(01)00058-2http://dx.doi.org/10.1016/S1383-5866(01)00058-2http://dx.doi.org/10.1016/S0926-3373(03)00024-9http://dx.doi.org/10.1016/S0926-3373(03)00024-9http://dx.doi.org/10.1016/S0926-3373(03)00024-9http://dx.doi.org/10.1016/j.tca.2005.11.008http://dx.doi.org/10.1016/j.tca.2005.11.008http://dx.doi.org/10.1016/j.tca.2005.11.008http://dx.doi.org/10.1016/j.fuproc.2005.06.001http://dx.doi.org/10.1016/j.fuproc.2005.06.001http://dx.doi.org/10.1016/j.fuproc.2005.06.001http://dx.doi.org/10.1016/j.fuproc.2005.06.001http://dx.doi.org/10.1016/j.tca.2005.11.008http://dx.doi.org/10.1016/S0926-3373(03)00024-9http://dx.doi.org/10.1016/S1383-5866(01)00058-2http://dx.doi.org/10.1016/j.fuel.2004.06.016http://dx.doi.org/10.1016/j.supflu.2006.03.007http://dx.doi.org/10.1016/j.fuel.2005.08.004http://dx.doi.org/10.1016/S0920-4105(01)00162-0http://dx.doi.org/10.1016/j.cattod.2006.09.037http://dx.doi.org/10.1016/j.wear.2004.11.009http://dx.doi.org/10.1016/S0009-2509(01)00337-2

recovery of used lubricant oils through adsorption of residues on solid surfaces word

Documents